Sensor Control Circuit for Power-Off Current Sneak Prevention
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Solution Overview
Problem
Conventional control circuits allow current to sneak from the signal line to the power line during power supply disconnection, resulting in intermediate potential output, which can damage the LSI internal circuit and cause erroneous signal diagnosis.
Innovation Solution
A control circuit design that includes a load between the power and signal lines, with first and second transistors and a gate control circuit to turn off the transistors during power supply disconnection, preventing current flow through the use of a second NMOS transistor and a third PMOS transistor to connect the gate terminals of the first and second PMOS transistors to the signal line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate terminals of the first and second transistors are connected to ground to protect against reverse connection, then reverse connection protection is achieved, but at the time of power supply disconnection the transistors turn on causing current to sneak from signal line to power line
Solution Approach 1:
The patent applies dynamics by making the gate terminal connections dynamic rather than static. The gate terminals are connected to ground during normal operation for reverse protection, but automatically connected to the signal line when power supply is detected as disconnected, thereby dynamically changing the transistor state from on to off to prevent current sneaking. This is achieved through a detection circuit that monitors power supply status and controls the gate connections accordingly.
Solution Approach 2:
The patent introduces an intermediary detection circuit and control mechanism between the power supply and the transistor gate terminals. This intermediary component detects power supply disconnection and mediates the connection switching between ground and signal line for the gate terminals, thereby preventing the harmful effect of current sneaking without compromising reverse connection protection.
2Ease of operation
If the first and second transistors remain on during power supply disconnection to maintain signal path, then signal transmission is maintained, but current sneaks from signal line to power line causing intermediate potential output that can damage LSI internal circuit
Solution Approach 1:
The patent applies preliminary anti-action by detecting power supply disconnection in advance and proactively switching the gate terminal connections to prevent current sneaking before it occurs. The detection circuit monitors power supply status and preemptively changes the transistor state to off, thereby preventing the harmful intermediate potential from developing and damaging the LSI internal circuit.
Solution Approach 2:
The patent makes the transistor state dynamic based on power supply status. Instead of maintaining a fixed on-state during power disconnection, the system dynamically switches to off-state when power disconnection is detected, thereby adaptively preventing harmful effects while maintaining signal transmission during normal operation.
Data Source
AI summary
To prevent an output of an intermediate potential by suppressing sneaking of a current from a signal line to a power line at the time of disconnection of a power supply. A control circuit which receives a power supply voltage from a power line L11 and outputs an output signal to a signal line L12 includes: a load R11 which is provided between the power line and the signal line; a first transistor P11 which is provided between the load and the signal line; a second transistor P12 which is provided between a well of the first transistor and the power line; and a gate control circuit 15 which connects a gate terminal of the first transistor and a gate terminal of the second transistor to the signal line and turns off the first transistor and the second transistor, at the time of disconnection of a power supply.